Chemical modification of viscose fibres by adsorption of carboxymethyl cellulose and click chemistry

Abstract

Functionalization of cellulosic materials to achieve new and advanced properties is a widely explored research area. This thesis is focused on the novel approach for modification of cellulosic materials by the combination of adsorption of carboxymethyl cellulose (CMC) onto cellulose surface and the copper-catalyzed azide-alkyne cycloaddition (CuAAC) “click” reaction.

The literature part gives an overview on the basics of cellulose chemistry, chemical functionalization of cellulose, as well as explains the principle of the chemical conjugation of carboxylic groups obtained by formation of amide bonds. The chapter continues with the phenomenon of the polyelectrolyte adsorption onto cellulose, takes a look at the viscose production process and, finally, it introduces the novel field of “click” chemistry.

In the experimental part, methods and techniques applied are described. The experimental part focuses on the evaluation of the adsorption efficiency of CMC and its derivatives onto viscose in different reaction conditions, as well as on examination of chemical and mechanical stabilities of the modification. CMC functionalization was analyzed with spectroscopic techniques and elemental analysis. The effect of various reaction conditions on adsorption was studied and quantified by means of the phenol-sulphuric acid method for the estimation of total adsorbed carbohydrates. Chemical and mechanical stabilities of the modified CMC and fibres were studied by the alkaline and wet frictional treatments, respectively.

The main findings revealed that chemically modified viscose fibres (cellulose II) behave differently from cellulose wood pulp and cotton (cellulose I) in respect of polysaccharide adsorption. The functionalization of CMC resulted in clear changes in the molecular structure of CMC, appearing as an increase in nitrogen content. In addition, spectroscopic analyses revealed characteristic signals of alkyne, azide and amide bonds indicative of successful grafting reactions. Adsorption of CMC onto viscose fibres was studied with Raman spectroscopy and x-ray photoelectron spectroscopy (XPS), and revealed changes on the surface of the viscose. The click reaction was demonstrated via fluorescent labelling. Moreover, the study on chemical and mechanical stabilities showed reasonable results. In general, combination of polysaccharide adsorption and click chemistry can be considered as a promising method for introducing new functionalities to the viscose fibres.